1. Field of the Invention
The present invention relates to a donor substrate, a method of fabricating a donor substrate, and a method of fabricating an organic light emitting display (OLED) and, more particularly, to a method of fabricating a patterned donor substrate and a method of fabricating an OLED using the patterned donor substrate.
2. Description of the Related Art
Among flat panel displays (FPDs), an organic light emitting display (OLED) is an excellent type of FPD for displaying moving images of all sizes because the OLED has a fast response speed of 1 ms or less, consumes a small amount of power, and is an emissive type of display allowing for a wide viewing angle. Also, the OLED can be fabricated at low a temperature via a simple process based on conventional semiconductor manufacturing technology. For these reasons, the OLED has attracted much attention as the next-generation FPD.
The OLED can essentially be classified into a polymer device made by a wet process and a small molecular device made by a deposition process, according to the types of material and processes used for the emission layers of an organic light emitting diode. Two drawbacks of the inkjet wet process is that 1) organic layers other than the emission layer can essentially be formed of only limited kinds of materials, and 2) it is difficult to form a structure on a substrate using the inkjet method. A drawback of the deposition method is that it is difficult to fabricate a large-sized device using a metal mask.
As an alternative to the inkjet method and the deposition method, a laser induced thermal imaging (LITI) process has recently been developed. In the LITI process, laser beams irradiated by a light source are converted into thermal energy, and a patterned material on a donor substrate is transferred to an acceptor substrate using the thermal energy, thus forming a pattern on the acceptor substrate.
When the transfer layer of the donor substrate is transferred using the LITI process, it is transferred onto all portions of the acceptor substrate because all portions are irradiated with laser beams. Thus, the transfer layer is formed on portions of the acceptor substrate that do not need the transfer layer, such as on the encapsulation portion.
Since the transfer layer is an organic material, the presence of the transfer layer in the encapsulation portion can lead to poor adhesion of sealant in the encapsulation portion. Poor adhesion of sealant in the encapsulation portion allows external gas and moisture to be introduced into the OLED, thus shortening the lifetime of the emission layer of the OLED, leading to pixel failure. As a result, LITI produced emission layers require an extra process of removing portions of the transfer layer transferred to the encapsulation portion of the acceptor substrate.
In order to remove the transfer layer from the encapsulation portion, an additional apparatus, such as a mechanical shutter or modulator, can be installed as an on-off controller for the laser, so that the transfer layer can be patterned according to an on-off state of the laser. Also, since a modulator needs a high power laser, a significant increase in manufacturing cost is incurred. However, the mechanical shutter operates at low speed, leading to a failure in the pattern. Further, on-off operations of the laser leads to increased process time. What is needed is an improved method of making a donor substrate that prevents the transfer layer from transferring onto the encapsulation portion of the acceptor substrate while avoiding the use of an on-off controller for a laser.